1. Field
The present disclosure relates generally to communication systems, and more particularly, to an apparatus and method for pre-charging a crystal oscillator.
2. Background
A wireless device (e.g., a cellular phone or a smartphone) may transmit and receive data for two-way communication with a wireless communication system. The wireless device may include a transmitter for data transmission and a receiver for data reception. For data transmission, the transmitter may modulate a transmit local oscillator (LO) signal with data to obtain a modulated radio frequency (RF) signal, amplify the modulated RF signal to obtain an output RF signal having the desired output power level, and transmit the output RF signal via an antenna to a base station. For data reception, the receiver may obtain a received RF signal via the antenna, downconvert the received RF signal with a receive LO signal, and process the downconverted signal to recover data sent by the base station.
The wireless device may include one or more oscillators to generate one or more oscillator signals at one or more desired frequencies. The oscillator signal(s) may be used to generate the transmit LO signal for the transmitter and the receive LO signal for the receiver. The oscillator(s) may be required to generate the oscillator signal(s) to meet the requirements of the wireless communication system with which the wireless device communicates.
Clock generators may receive oscillator signals from an oscillator and may generate clock signals for various modules within the wireless device. The oscillator may be a crystal oscillator, which is typically slow to settle at start-up. Since the wireless device may operate intermittently, additional start-up time may result in additional power being undesirably dissipated. Accordingly, an apparatus and method is needed for pre-charging the crystal oscillator to accelerate start-up.